Relationship between critical current and flux-flow resistivity in the mixed state of Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$

Abstract

We studied the temperature and magnetic field dependence of vortex dissipation and critical current in the mixed-state of unconventional superconducting alloys Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ ($0.044\le x\le 0.100$) through current-voltage measurements. Our results reveal that all the electric field $E$ vs current density $j$ curves in the Ohmic regime merge to one point ($j_0,E_0$) and that there is a simple relationship between the critical current density $j_c$ and flux-flow resistivity ${\rho }_{\mathrm{ff}}$: ${\rho }_{\mathrm{ff}}/{\rho }_{\mathrm{n}}=(1-j_c/j_0{)}^{-1}$, where ${\rho }_{\mathrm{n}}=E_0/j_0$ is the normal-state resistivity just above the superconducting transition. In addition, $E_0$ is positive for all five dopings, reflecting the abnormal behavior of the flux-flow resistivity ${\rho }_{\mathrm{ff}}$: it increases with decreasing magnetic field. In contrast, $E_0$ is negative for the conventional superconductor Nb since, as expected, ${\rho }_{\mathrm{ff}}$ decreases with decreasing magnetic field. Furthermore, in the under-doped and over-doped single crystals of Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$, the parameter $E_0$ remains temperature independent, while it decreases with increasing temperature for the single crystals around optimal doping ($0.060\le x\le 0.072$). This result points to the co-existence of superconductivity with some other phase around optimal doping.

6 pages, 6 figures

References in corpus (8)

• Evidence for an electron nematic phase transition in underdoped iron pnictide superconductors
• Effects of Co substitution on thermodynamic and transport properties and anisotropic $H_{c2}$ in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ single crystals
• Determination of the phase diagram of the electron doped superconductor Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Vortex phase diagram of Ba(Fe0.93Co0.07)2As2 single crystals
• Spin susceptibility, phase diagram, and quantum criticality in the electron-doped high Tc Superconductor Ba[Fe(1-x)Co(x)]2As2
• Structural and magnetic phase transitions near optimal superconductivity in BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$
• Short-range cluster spin glass near optimal superconductivity in BaFe${}_{2-x}$Ni${}_x$As${}_2$
• Exceptional Suppression of Flux-Flow Resistivity in FeSe${}_{0.4}$Te${}_{0.6}$ by Back-Flow from Excess Fe Atoms and Se/Te Substitutions